"Capt. Geoffrey Thorpe" The Sea Hawk at wow way d0t com writes:

Now, all of this raises a couple of question. Exactly what is the
ammeter for if I wasn't showing any sign of discharge on a battery not
running full tilt?

The [zero-center style] ammeter tells you what is going in or out
of the battery. It tells you if the alternator is working - it tells
you nothing [directly] about the condition of the battery.

[added]

But you can infer battery condition by observing trends.

Normally, at initial idle, the ammeter will show a loss; the alternator
is making less than needed and the battery is helping.

At runup, the ammeter will show a charge. This will hold true at taxi,
etc.

Eventually, the charge expended by starting/idle will be recouped
and the ammeter will center near zero. BUT exactly when happens
that, be it one min. after TO, or 10 or 100, is a function of many
things including other loads, how long it took to crank, age of the
battery, etc. But it's your bird, and it should act about the
same in the same circumstances.

1) If the battery is run down, say because you are a slacker and
did NOT go flying last week; there's more charging needed.

2) If the battery is barely run down at all, because you stopped for
fuel & the restart was warm & easy; it may recharge during that long
taxi.

3) When the battery gets really whipped, it won't take a charge;
i.e. it appears to recharge in far less time.

The "no crank" you experienced means insufficent voltage at the
starter innards. Its cause could be: discharged/bad battery [low
source voltage] or bad connections -- be they at the battery terminals,
the starter cables, the solonoid, or inside the starter.

I always suspect the grounds first, but YMMV.





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